The Plum Orchard Harvest Display

A Growing Display for the Plum Harvest

At the end of summer, the Willowbend Plum Orchard prepares for its harvest festival. The orchard educator wants a small growing display beside the tasting tent. The display should help visitors understand how a plant adds new material as it grows. The educator must decide whether to use orchard soil or a soil-free setup.

A student research team planted matched young plum plants in three indoor boxes. The plants were the same kind and about the same size. Each plant received the same amount of light and the same temperature. The team measured dry plant mass at the beginning and after eight weeks. Dry mass was used so that water held in a plant would not make one plant seem to have added new material just because it had recently been watered.

Box A contained orchard soil, normal air, and a regular water supply. Box B contained washed gravel instead of soil. Its roots received water with the small amounts of dissolved mineral nutrients needed for healthy growth, and the box had normal air. Box C contained orchard soil and regular water, but its air had much less carbon dioxide than normal air. The team kept the other conditions as similar as possible.

The team also weighed the dry soil in Box A before and after the test. A short research note explained that carbon dioxide in air contains carbon that plants can use to build plant parts. Water supplies material used in plant growth, and dissolved minerals are needed in smaller amounts for plant functions. The study could compare total dry-mass changes, but it could not assign an exact number of grams to each source.